In order to reduce a load of signaling of a core network, a communication system of LTE (Long Term Evolution) enables a mobile station UE in a RRC_CONNECTED state (a connected state) to enter a DRX (Discontinuous Reception) state (an intermittent reception state) without transition to a RRC_IDLE state (an idle state).
In certain situations such as disasters, concert venue, and fireworks venue, a large number of mobile stations UE in the DRX state try to perform call origination processing and thereby cause burst traffic.
The mobile station UE executes a RA (random access) procedure (a RA procedure), specifically, “Contention based RA procedure”, with a radio base station eNB, when the mobile station UE in the DRX state returns to a non-DRX state (a continuous reception state) to perform call origination processing.